In the oil and gas industry it is often desirable to stimulate a well by introducing a high pressure proppant laden fluid into the well bore. The fluid may include water or diesel, which may be in the form of a gel or foam, while the proppant may commonly be sand or bauxite, although many other proppants are known and used.
Pressures on the order of 5,000 to 12,000 psi are often required to fracture a formation and are supplied by above ground pumping equipment such as a HT-400 triplex pumping unit as illustrated on pages 2414, 2415 and 2418 of Halliburton Services Sales and Service Catalog, volume 43.
After the formation is fractured, the proppant remains in the fracture itself, while the fluid is retrieved, or allowed to dissipate within the formation. The proppant then acts to hold the fracture open such that a channel is maintained which enhances the flow of hydrocarbons from the producing formation to the well bore. The success of the stimulation operation often depends upon the ability of the proppant to maintain the fracture in an open position. Therefore, it would be desirable to have a laboratory testing unit which will simulate a fracturing operation and provide results prior to the actual stimulation operation. In particular, an in-situ test cell which could utilize actual core samples and simulate actual downhole temperature, permeability, conductivity and fluid migration characteristics would be extremely useful to the oil and gas service industry.
In a paper prepared for a joint Society of Petroleum Engineers/Department of Energy Symposium entitled "Long-Term Performance of Proppants Under Simulated Reservoir Conditions", number 16415, by M. G. Mach and G. S. Penny, a standard American Petroleum Institute test cell has been modified for use in in-situ type conditions. FIG. 1 illustrates how holes were drilled into the pistons and how ring type seals are used to seal around the piston. Further, a glue type sealant must be used to prevent fluid loss from occurring around the outside edge of the core samples.
Additionally, U.S. Pat. No. 4,562,726 to Barnaby shows an apparatus for testing the compressability of a single formation core sample. The test apparatus includes a sleeve which seals the core sample when pressurized fluid is supplied to a surrounding annular space. Similarly, Braver et al, U.S. Pat. No. 4,599,891, describes a core holder for a single core sample having a sleeve which seals the sample when pressurized fluid is introduced to the surrounding annulus and a radial force is applied therearound. The sleeve provides a seal around the core, moveable plug and a fixed plug.
Therefore, a need exists for a device such as the present invention, as described herein, which utilized a settable packer to seal around the core samples, pistons and proppant bed such that more reliable results are obtained than are presently possible with the prior art test devices.